Method and apparatus for roll forming ends of helically corrugated pipe

ABSTRACT

Method and apparatus for forming one or more annular corrugations and a flange on the ends of a length of helically corrugated pipe. The method involves forming the two ends, one at a time. The trailing end of the pipe, as it comes from a pipe forming machine or the like, is located axially in a predetermined relation to a forming apparatus, and the trailing end is formed while the length of pipe is backed up under pressure on the leading end and is supported intermediate its ends. Rotational force is applied to both ends of the pipe to avoid distortion. Thereafter, the leading end is formed while the length of pipe is backed up under pressure on the trailing end and is supported intermediate its ends; and again rotational force is applied to both ends of the pipe. The apparatus comprises two units in tandem, disposed parallel to the pipe axis, and the pipe is moved, transversely of its axis, successively to the two units. In the first unit a forming section is in a fixed position, and a back-up and thrust section and an intermediate pipe supporting section are movable in a 2:1 ratio to take care of different pipe lengths. In the second unit, a back-up and thrust section is in a fixed position, and a forming section and an intermediate pipe supporting section are arranged as above described, to take care of different lengths of pipe.

United States Patent Lewis 51 May 16, 1972 [54] METHOD AND APPARATUS FOR ROLL FORMING ENDS OF HELICALLY CORRUGATED PIPE Clarence P. Lewis, Carlisle, Ohio Armco Steel Corporation, Middletown, Ohio [22] Filed: Oct. 7, 1970 [21] Appl.No.: 78,892

[72] Inventor:

[73] Assignee:

[52] U.S. Cl ..72/105, 72/370 3,548,623 l2/l970 Hess et a] ..72/l06 Primary Examiner-Lowell A. Larson Anomey-Melville, Strasser, Foster & i-lofiman [57] ABSTRACT Method and apparatus for forming one or more annular corrugations and a flange on the ends of a length of helically corrugated pipe. The method involves forming the two ends, one at a time. The trailing end of the pipe, as it comes from a pipe forming machine or the like, is located axially in a predetermined relation to a forming apparatus, and the trailing end is formed while the length of pipe is backed up under pressure on the leading end and is supported intermediate its ends. Rotational force is applied to both ends of the pipe to avoid distortion. Thereafter, the leading end is formed while the length of pipe is backed up under pressure on the trailing end and is supported intermediate its ends; and again rotational force is applied to both ends of the pipe.

The apparatus comprises two units in tandem, disposed parallel to the pipe axis, and the pipe is moved, transversely of its axis, successively to the two units. in the first unit a forming section is in a fixed position, and a back-up and thrust section and an intermediate pipe supporting section are movable in a 2:1 ratio to take care of difierent pipe lengths. In the second unit, a back-upand thrust section is in a fixed position, and a forming section and an intermediate pipe supporting section are arranged as above described, to take care of different lengths of pipe.

16 Claims, 15 Drawing Figures PATENTEDHAY 16 I972 3, 662,579

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ATTORNEYS PATENTEDIMY 16 I972 SHEET 7 [1F 9 INVENTOR/S CLAQENCE P LEW/s,

I] ATTOR NEYS ma L flaw 3% PATENTEDMAY 16 1912 SHEET 8 [IF 9 9' J1" M2 M1 MOTOR MOTOR AUTO W HAND KLS RAP/0 TEAM INVENTOR/ M um w m M w M H M m m S A H 2 T 5 2 o D i N A z r PN w ml- I 1 r 0% M I W 1 H N c G 1 A 5 20, T E L E E n r c n H i #M 4 m2 y W L SE V m 14A m ym My ATTO/RNEYS i n BRIEF SUMMARY OF THE INVENTION Large quantities of helically corrugated pipe are currently being produced for various uses. It is desirable to be able to join sections of such helically corrugated pipe end to end and a way of accomplishing this is by means of a hugger band, as taught in the Boynton U.S. Patent No. 3,501,179. In order to use such a hugger band for joining adjacent ends of helically corrugated pipe, it is necessary to form annular corrugations and perhaps also a flange in each end of each section of such helically corrugated pipe.

Various attempts have been made to form these annular corrugations and they have uniformly involved attempts to so corrugate both ends of a piece of pipe at the same time. All such prior attempts have proved unsuccessful for various reasons. The primary reason is that the pipe has helical corrugations so that when it is attempted to roll form an annular corrugation there is a tendency at one end of the pipe to screw itself into the roll fon'ning unit as it rotates and at the other end there is a tendency for the pipe to screw itself out of the roll forming unit as it rotates. Additionally, as the pair of forming rolls encounter a helical corrugation, there is a tendency to shift the pipe axially in one direction as the rolls encounter the rise of a corrugation and to shift the pipe axially in the other direction as the rolls encounter the reverse side of a corrugation. It has been impossible thus far to solve the problem of these axial shifts and thrusts engendered by the fact that the pipe has helical corrugations.

According to the present invention, therefore, each end of the pipe is formed separately. Two forming units are disposed in tandem parallel to the pipe axis and the pipe is moved transversely of its axis, first into one unit where one end of the pipe is roll formed and then into the second unit (which is in efi'ect reversed end for end from the first unit) and the other end of the pipe is roll formed in the second unit. v

In order to avoid the various complications discussed above, means are provided to support the pipe being formed intermediate its ends and preferably centrally thereof and means are provided to drive the end of the pipe which is not being formed in the particular unit at the same speed as the other end of the pipe is being driven by the forming rolls to avoid twisting of the pipe. At the same time, the end of the pipe not being formed in the particular unit is backed up under pressure axially of the pipe to prevent the axial shifting of the pipe during roll forming.

Conveniently, the apparatus of the present invention may be set up adjacent the end of the pipe forming machine and as the pipe issues from the pipe forming machine and is cut to length in one of a number of ways, means are provided to stop the axial movement of the pipe with its trailing end short of a predetermined transverse line. The pipe is kicked off transversely of its axis in well known manner into a positioning unit where the trailing end of the pipe is brought accurately to said predetermined line. From the positioning unit, the pipe is again kicked off transversely of its length into the first unit in which the roll forming section is fixed in position with respect to the said predetermined line. In the first unit, an intermediate pipe supporting section and a back-up and thrust section are adjustably mounted to take care of different lengths of pipe; and the adjustment of these two sections is arranged such that the back-up and thrust section moves twice as far as the intermediate pipe supporting section, whereby the latter is always disposed centrally of the length of pipe regardless of its length.

Means are provided at the back-up and thrust section to push the length of pipe axially into the forming rolls of the forming section and to apply a thrust axially of the pipe. The forming section has a pair of forming rolls which are power driven and means are provided to force one of said rolls into an engagement with the pipe against the other fonning roll. The initial deformation is made without rotating the pipe.

Thereafter the forming rolls are driven, and a pair of rolls in the back-up and thrust section are driven at the same speed, to roll form the trailing end of the length of pipe.

Means are provided to eject the pipe from the roll forming section and to kick it over into the second unit in which the roll forming section (now movable) and the back-up and thrust section (now fixed) are reversed end for end; and in the second unit, the leading end of the length of pipe is roll found as described above.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a fragmentary cross sectional view of the abutting ends of two pieces of helically corrugated pipe showing the configuration produced by the present invention.

FIG. 2 is a diagrammatic phantom view of one of the units of the apparatus.

FIG. 3 is a diagrammatic plan view of the arrangement of the apparatus.

FIG. 4 is a diagrammatic sectional view taken on the line 44 of FIG. 3 on an enlarged scale.

FIG. 5 is a fragmentary perspective view of the drive and locking means for the movable sections of the machine.

FIG. 6 is a longitudinal cross sectional view through the roll forming section of one of the units.

FIG. 7 is a longitudinal cross sectional view through the back-up and thrust section of one of the units.

FIG. 8 is an elevational view of a central supporting section.

FIG. 9 is a fragmentary cross sectional view taken on the line 9 -9 of FIG. 8.

FIG. 10 is a fragmentary cross sectional view taken on the line l0-l0 of FIG. 8.

FIG. 11 is a cross sectional view taken on the line I1--ll of FIG. 6.

FIG. 12 is a elevational view as seen from the left of FIG. 6.

FIG. 13 is a hydraulic diagram; and

FIGS. 14A and 14B, taken together, are an electrical diagram.

DETAILED DESCRIPTION An exemplary embodiment of an apparatus for carrying out the above entitled method will now be described with reference to the drawings.

The general arrangement of the apparatus is best seen in FIG. 3. The line 10 in FIG. 3 indicates the path of travel of the axis of a piece of pipe coming off a pipe forming machine or other pretreatment apparatus assumed to be off the drawing to the right. The pipe comes of? such previous apparatus in the direction of the arrow on the line 10. The line 11 indicates a position line for the trailing end of the length of pipe. A positioning apparatus is generally indicated at 12 and a first unit of the machine is shown at 13 and a second unit at 14. The unit 13 comprises a roll forming section 15, a back-up and thrust section 16, and a central supporting section 17. The unit 14 includes the same sections but reversely positioned. Thus, in the unit 14 the roll forming section is at the other end of the unit and the back-up and thrust section 16a is at the end corresponding to the unit 15. The central supporting section is again at the center.

Means (not shown) are provided to stop the pipe on its runout from prior apparatus so that its trailing end is somewhat short of the line 11. Conventional kickers are provided to roll the pipe transversely of its axis into the positioning unit 12. In FIG. 4, it will be seen that the positioning unit comprises a number of V-shaped anns l8 pivoted at 19 and provided with means (not shown) for rotating the arms 18 counterclockwise as seen in FIG. 4 to roll the pipe from the positioning unit to the first forming unit. The pipe is indicated in broken lines at 20. A positioning cylinder is provided at 21 having a fixed stroke such that it pushes the length of pipe axially to a position where its trailing end is on the line 11.

As soon as the length of pipe is properly positioned axially, the arms 18 are actuated to roll the pipe transversely of its length into the first roll forming unit 13. As will be described in moredetail hereinafter, the pipe is roll formed at its trailing end in the section 15 of the unit 13 and is then kicked over, as will also be described, into the unit 14. In the unit 14 the leading end of the pipe is roll formed in the section 15a. The pipe is then kicked off transversely of its length for any further processing which may be required.

The Roll Forming Section Reference will now be made to FIGS. 6, 11 and 12. From these Figures it will be seen that the upper forming roll 30 is mounted on a shaft 31 which is driven through gearing 32 by an electric motor or the like 33. The lower forming roll 34 is mounted between bearings 35 and 36 on a frame 37 which may be raised and lowered by hydraulic pressure applied to the cylinder 6. The drive for the lower roll 34 is obtained through gearing 39 from the upper forming roll shaft 31 to the shaft 40. The shaft 40 drives the lower forming roll 34 through a Schmidt coupling 44. The Schmidt coupling is a well known mechanism for transmitting rotational drive from a fixed shaft to a non-coaxial parallel shaft which must be subjected to movement transversely of its axis. This coupling is necessary in the structure herein disclosed so that the lower forming roll 34 may be moved upward against the upper forming roll 30. As best seen in FIG. 12, there are provided in connection with the upper forming roll 30 the back-up bearings 41 against which the trailing end of the pipe is thrust. In FIG. 12 the outline of the trailing end of the pipe is indicated by the broken line 42 and it will be understood that the bearings 41 are adjustable so as to take care of pipe of different diameter. Back-up and Thrust Section A back-up and thrust unit is best seen in FIG. 7. It will be observed that it is mounted on wheels 50 arranged to ride on rails 51 for a reason which will be described hereinafter. The carriage on which the back-up and thrust unit 16 is mounted is moved along the rails by means of a rack and pinion arrangement including a rack 52 and pinion 53.

The unit 16 comprises a lower roll 54 which is driven by means of an electric motor 55 on a fixed axis. The roll 54 is preferably covered with neoprene or rubber or rubber-like material for the purpose of enhancing friction. A cooperating upper roller 56 is an idler and it is advanced and retracted on its axis by the action of the cylinder 3 and its piston rod 3a. It should be noted that the roll 54 is driven at the same speed as the lower forming roll 34 so that the same torque is applied at both ends of the pipe to avoid twisting. The upper roll 56 does not in any sense deform the leading end of the pipe but simply serves to hold the pipe against the roll 54 so as to be driven thereby frictionally.

The Central Supporting Section The central supporting section 17, as can be seen with reference to FIGS. 2 and 8 to inclusive, comprises two pairs of arms in V configuration as indicated at 60 in the several Figures. The two sets of arms 60 are rigidly secured together by means of a connector member 61 which may be a piece of welded steel pipe to which the arms 60 are welded. The arms 60 are provided with rollers 62a to support smaller diameter pipe such as indicated in phantom lines at 42a and rollers 62 to support large diameter pipe such as indicated in phantom lines 42. The section 17 is also mounted on wheels 63 riding on rails 64 which may of course be the same rails or a continuation of the rails 51 previously described. Similarly, a rack 65 is provided which again may be a continuation of the rack 52 heretofore described, and as seen in FIG. 10 a pinion 66 driven through gearing 67 by a motor 68 is provided.

From the foregoing description it will be seen that in the unit 13 the sections 16 and 17 may be adjusted axially of the pipe to take care of different lengths of pipe. Each of the sections 16 and 17 has its own motor to drive a pinion in engagement with a rack which may of course be a continuous rack. The drives are so arranged that the section 17 moves half the distance movedby the section 16 for each revolution of the respective pinions, whereby the section 17 will always be centrally disposed between the sections and 16. This may be accomplished by a 2:1 ratio in the respective gear drives, or by having one motor designed to run twice as fast as the other. The same situation prevails in the unit 14 except in the unit 14 it is the roll forming section 15a which is movable rather than the back-up and thrust section 16a. Once the respective sections have been adjusted for the length of pipe to be formed, the sections are locked in position, as seen in FIG. 5, by means of a locking element 69 which is simply a mating piece of rack which is actuated by a piston of cylinder 70 to lock the adjustable sections of the unit in adjusted position.

Means are provided to rock the arms 60 and these comprise an arm welded or otherwise, rigidly secured to the member 61 and acted upon by the pistons of the two cylinders l and 2. These cylinders are shown in more detail in FIG. 9. It will be seen that the pistons of both cylinders are connected to the lower end of the member 80 so that it may be moved either to the right or to the left of FIG. 9. The piston rod la of the cylinder 1 is moved when pressure is supplied to the cylinder 1 against a stop 81. The piston rod 2a of the cylinder 2 is not limited in its stroke. As will be described in more detail hereinafter, fluid at higher pressure is applied to the cylinder 1 than to the cylinder 2. Operation of a Unit Reference is now made to FIG. 2 which, as indicated, is a phantom view of the unit 13 and which shows a number of hydraulic cylinders and a number of limit switches in various positions. The interrelationship of the various cylinders in the hydraulic circuit will be understood with reference to FIG. 13 and the interaction of the limit switches by reference to FIG. 14. The general sequence of operations will be best understood by reference to FIG. 2. Let it be assumed that the piston of cylinder 1 is extended against its stop and the piston rod of cylinder 2 is retracted whereby the arms 60 are tilted toward the viewer as seen in FIG. 2. The piston rod of cylinder 3 is retracted, moving the upper roll 56 back out of the way to permit entry of a piece of pipe. The piston rod of cylinder 4 is also retracted thus raising the roll 56. The piston rods of the cylinders 5 are retracted, the piston rod of cylinder 6 is retracted, and the piston rods of cylinders 7 are retracted. The unit is now in a position to receive a length of pipe to be operated upon. As a piece of pipe rolls from the positioning unit 12 into the unit 13, it contacts the limit switch A. This causes hydraulic fluid to be applied to the cylinder 2 to extend its piston rod and, through the lever 80, to rotate the arms 60 to their erect position shown in FIG, 2. Since the piston of cylinder 1, which is the higher pressure cylinder, is extended against the stop 81, the piston rod of cylinder 2 moves until it abuts or is stopped by the rod of piston 1.

At this point, the limit switch B (or if desired, a time delay in association with limit switch A) actuates the cylinder 3 to push the roll 56 and its associated parts to the right. As will have been observed, the roll 56 has a flange 56a which bears against the leading end of the length of pipe and thus the cylinder 3 serves to push the length of pipe axially toward the right, as seen in FIG. 2, into the bite of the forming rolls 30 and 34. Preferably, the cylinder 3 is arranged to provide a rapid advance at approximately 1,500 psi for about 10 inches and thereafter a slow advance for approximately 3 inches. Cylinder 4 is then actuated by the limit switch C and its piston rod extends and causes the upper roll 56 to move downward to contact the inside of the pipe. It will be noted that the pipe has been pushed axially against the bearing members 41 and after a predetermined length of travel limit switch D is actuated, which switches the valve for cylinder 3 to a neutral or hold position and causes the rods of the cylinders 5 to extend and drop the wedges 5a into the slots 7a to mechanically hold the bearings 41 in position. Cylinder 6 is also caused to function by limit switch D to raise the lower forming roll 34 into operating position. At this point the upper and lower forming rolls 30 and 34 are not rotating and the initial deformation of the trailing end of the pipe is simply a pressing operation. As the lower roll 34 contacts limit switch E, it actuates the valve for the cylinder 3 to low pressure system which may be on the order of 300 psi and may be adjustable for pipe gauge and weight. This pressure is maintained through the rolling operation.

At this point in the operation then, the rods of cylinders 1, 3, 4, 5 and 6 are extended, the rod of cylinder 2 is extended approximately half its stroke, and the rods of the cylinder 7 are retracted. The forming operation now takes place with the forming rolls 30 and 34 being driven and the supporting roll 54 being driven at the same speed. In actual practice, a 50 horsepower gear motor has been used having a 45 rpm output. With such a motor, the time required to roll a piece of 12 inch pipe one revolution is approximately 6 seconds. While rotation may be controlled in various ways, a preferred way is by means of a pulse counter which registers the passage of the pipe corrugations and stops the motor after nine counts, nine counts being the conventional number of helical corrugations in helically corrugated pipe.

Upon a signal from the pulse counter that the forming operation has been completed, the piston of the cylinder 4 is retracted to open or raise the upper back-up roll 56. The cylinders 5 retract their pistons to retract the wedges 5a. The cylinder 6 retracts the lower forming roll 34 and the cylinder 3 retracts the back-up roll 56 at rapid traverse. The lower forming roll contacts limit switch F which causes the cylinders 7 to be actuated to push the pipe to the left out of the section and these cylinders then retract upon contacting the limit switch G. The limit switch F on the back-up unit is in series with the limit switch F to assure that the rolls are clear of the pipe. Limit switch F also causes actuation of the cylinder 1 to retract its piston and permit cylinder 2 to cause its piston to complete its stroke which rocks the assembly of the arm 60 away from the viewer as seen in FIG. 2 to roll the pipe out of the unit. As the pipe rolls clear of the arms 60, it contacts the limit switch H and cylinder 2 then retracts, and cylinder 1 extends to the position originally described and the cycle is complete.

The description of the operation of unit 13 is the same as with unit 14 except that the position of the forming section (now movable) and the back-up section (not fixed) are reversed. The operation of the unit 14 need therefore not be described in detail except to say that the unit 14 forms the desired corrugations on the leading end of the length of pipe.

FIG. 1 shows in enlarged cross section the abutting ends of two pieces of helically corrugated pipe 90 and 91. The helical corrugations of the length 90 are shown at 92 and typically there may be formed two annular corrugations 93 and an annular inwardly directed flange 94. Two adjacent ends of pipe formed as above described may be connected together by hugger band 95 with gaskets 96 as taught in the above mentioned Boynton patent.

The diagram of FIG. 13 shows the several cylinders which have been described, numbered with the same reference numerals used in FIG. 2. The hydraulic system employs an electric motor 100 to drive two pumps 101 and 102. In FIG. 3 conventional hydraulic symbols have been used and it is believed that the operation of the hydraulic circuit need not be described in detail but will be clear to one skilled in the art.

Similarly, in FIG. 14 the several limit switches are shown and are designated with the same numerals as those used in FIG. 2 and again it is believed that the electrical system does not require detailed explanation.

It is important to avoid deflection in the forming rolls and it will be clear that deflection of the shaft of the lower forming roll 34, as shown in FIG. 6, is avoided by providing the bearings 35, 36 on either side of the forming roll as a part of the unit which is raised by the cylinder 6. With regard to the upper fonning roll 30 deflection must be compensated by shimming. By reference to FIGS. 11 and 12, it will be noted that the roll supporting beam 31a is keyed into the side plates 31b as indicated at 31c. At its outboard end, the keying at 31d is provided with clearance so that shims may be inserted above and below the key to compensate for the amount of roll deflection encountered.

As the pipe end is deformed by the deforming rolls, the end of the pipe is pulled away from the bearings 41 but this reduction in length is taken care of by means of the wedge blocks 5a which cause the bearings 41 to back up the end of the pipe in its shortened condition.

The operation as described herein is operative through the major portion of the range of pipe diameters. When dealing with very small diameter pipe or very large diameter pipe, the wedge blocks must be withdrawn and pressure must be maintained on the cylinder 7 to perform the back-up function.

It will be understood that modifications may be made without departing from the spirit of the invention and no limitations not specifically set forth in the claims is intended or should be implied.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. Apparatus for annularly roll forming the ends of a length of helically corrugated pipe, comprising a. two units disposed in tandem, each unit comprising a roll forming section, a back-up and thrust section, and an intermediate pipe supporting section,

b. means to position a length of pipe to be formed with one of its ends on a predetermined line transversely of the pipe axis,

c. the first of said units having its roll forming section fixed in relation to said predetermined line, for roll forming said one end of said length of pipe,

d. the second of said units having its back-up and thrust section fixed in relation to said predetermined line,

e. said units being thus reversed, end for end, for roll forming said one end in said first unit and the other end in said second unit, and

f. means to move said length of pipe transversely on its axis into said first unit and means for moving said length of pipe from said first to said second unit.

2. Apparatus according to claim 1, wherein said means to position one end of said length of pipe on a predetermined line is arranged to so position the trailing end of said length, in terms of its axial movement from another processing apparatus.

3. Apparatus according to claim 1, wherein the back-up and thrust section of said first unit and the roll forming section of said second unit are adjustable parallel to the pipe axis, to take care of different lengths of pipe to be formed.

4. Apparatus according to claim 3, wherein the inter- I mediate pipe supporting sections of both units are also adjustable.

5. Apparatus according to claim 4, wherein power means are provided to move said pipe supporting sections at half the speed of said back-up and thrust section of the first unit and roll forming section of the second unit respectively, whereby said pipe supporting sections will always be disposed centrally of the pipe being formed regardless of its length.

6. Apparatus according to claim 5, wherein each of said units is provided with an axially oriented rack, and each of said pipe supporting sections and the back-up and thrust section of the first unit and the roll forming section of the second unit are provided with a pinion engaging the respective rack, and a power means to rotate said pinion, the power means for said pipe supporting section being arranged to operate at half the rotational speed of the other sections, to drive said pipe supporting sections half the distance, per unit of time, of the other sections.

7. Apparatus according to claim 5, wherein each of said units is provided with an axially oriented rack, and each of said pipe supporting sections and the back-up and thrust section of the first unit and the roll forming section of the second unit are provided with a pinion engaging the respective rack, and a power means to rotate said pinion, the pinions for said pipe supporting sections having half the circumference of the others, to drive said pipe supporting sections half the distance of the other sections per revolution of the respective pinions.

8. Apparatus according to claim 1, wherein each of said roll forming sections comprises upper and lower cooperating forming rolls, means for driving the upper roll on a fixed axis, and means for driving the lower roll and means for moving said lower roll toward and away from said upper roll, means initially to press said lower roll against the pipe and the upper roll without rotation, and means operative upon completion of the initial local deformation, to cause said cooperationg rolls to rotate, to perform said annular roll forming operation.

9. Apparatus according to claim 8, wherein the said roll forming sections are provided with an end thrust bearing for the end of the pipe being formed, and means are provided to move said end thrust bearing axially of the pipe to compensate for the reduction in length resulting from the roll forming operation, and, upon completion of the forming operation, to push the pipe axially clear of the forming rolls.

10. Apparatus according to claim 8, wherein the lower forming roll shaft is provided with a bearing on each side of said roll to avoid shaft deflection, and wherein shim means are provided to compensate for deflection of the upper forming roll shaft.

11. Apparatus according to claim 1, wherein the back-up and thrust sections comprise a lower roll driven at the same speed as the lower forming roll of the respective unit, and an upper roll to hold the pipe against said lower driven roll, said upper roll having a flange to bear against the pipe end and having means to exert thrust against said pipe end.

12. Apparatus according to claim 11, wherein said lower roll is covered with a friction enhancing material.

13. Apparatus according to claim 11, wherein said upper roll is retractable for entry of the pipe into its unit and exit therefrom, and wherein means are provided to move said upper roll vertically and to press it against the inside of the pipe to press said pipe against said lower roll.

14. Apparatus according to claim 1, wherein said intermediate pipe supporting sections each comprise at least one pair of arms rigidly connected together in V" relation, means to tilt said arms in one direction to permit entry of a length of pipe, means to fix said arms rigidly in upright position to support said pipe, and means to tilt said arms in the other direction to permit said length of pipe to issue from said intermediate pipe supporting section.

15. Apparatus according to claim 14, wherein there are two pairs of said arms, said pairs being rigidly connected together and spaced apart axially of the pipe.

16. The method of annularly roll forming both ends of a length of helically corrugated pipe issuing axially from a pipe forming machine, which includes the steps of:

a. fixing the axial position of the trailing end of the length of b. feeding said length transversely of its axis into a first forming station, having a roll forming element fixed in relation to said trailing end,

0. annularly roll forming said trailing end while supporting said length of pipe intermediate its ends and rotationally driving said length at both ends, maintaining an axial thrust against the leading end of said length during said roll forming operation, feeding said length transversely of its axis into a second roll forming station, having a thrust element in fixed relation to said trailing end,

f. annularly roll forming said leading end while supporting said length intennediate its ends and rotationally driving said length at both ends, and

g. maintaining an axial thrust against said trailing end during said last named roll forming operation. 

1. Apparatus for annularlY roll forming the ends of a length of helically corrugated pipe, comprising a. two units disposed in tandem, each unit comprising a roll forming section, a back-up and thrust section, and an intermediate pipe supporting section, b. means to position a length of pipe to be formed with one of its ends on a predetermined line transversely of the pipe axis, c. the first of said units having its roll forming section fixed in relation to said predetermined line, for roll forming said one end of said length of pipe, d. the second of said units having its back-up and thrust section fixed in relation to said predetermined line, e. said units being thus reversed, end for end, for roll forming said one end in said first unit and the other end in said second unit, and f. means to move said length of pipe transversely on its axis into said first unit and means for moving said length of pipe from said first to said second unit.
 2. Apparatus according to claim 1, wherein said means to position one end of said length of pipe on a predetermined line is arranged to so position the trailing end of said length, in terms of its axial movement from another processing apparatus.
 3. Apparatus according to claim 1, wherein the back-up and thrust section of said first unit and the roll forming section of said second unit are adjustable parallel to the pipe axis, to take care of different lengths of pipe to be formed.
 4. Apparatus according to claim 3, wherein the intermediate pipe supporting sections of both units are also adjustable.
 5. Apparatus according to claim 4, wherein power means are provided to move said pipe supporting sections at half the speed of said back-up and thrust section of the first unit and roll forming section of the second unit respectively, whereby said pipe supporting sections will always be disposed centrally of the pipe being formed regardless of its length.
 6. Apparatus according to claim 5, wherein each of said units is provided with an axially oriented rack, and each of said pipe supporting sections and the back-up and thrust section of the first unit and the roll forming section of the second unit are provided with a pinion engaging the respective rack, and a power means to rotate said pinion, the power means for said pipe supporting section being arranged to operate at half the rotational speed of the other sections, to drive said pipe supporting sections half the distance, per unit of time, of the other sections.
 7. Apparatus according to claim 5, wherein each of said units is provided with an axially oriented rack, and each of said pipe supporting sections and the back-up and thrust section of the first unit and the roll forming section of the second unit are provided with a pinion engaging the respective rack, and a power means to rotate said pinion, the pinions for said pipe supporting sections having half the circumference of the others, to drive said pipe supporting sections half the distance of the other sections per revolution of the respective pinions.
 8. Apparatus according to claim 1, wherein each of said roll forming sections comprises upper and lower cooperating forming rolls, means for driving the upper roll on a fixed axis, and means for driving the lower roll and means for moving said lower roll toward and away from said upper roll, means initially to press said lower roll against the pipe and the upper roll without rotation, and means operative upon completion of the initial local deformation, to cause said cooperationg rolls to rotate, to perform said annular roll forming operation.
 9. Apparatus according to claim 8, wherein the said roll forming sections are provided with an end thrust bearing for the end of the pipe being formed, and means are provided to move said end thrust bearing axially of the pipe to compensate for the reduction in length resulting from the roll forming operation, and, upon completion of the forming operation, to push the pipe axially clear of the forming rolls.
 10. Apparatus according to claim 8, wherein the lower forming roll shaft is provided with a bearing on each side of said roll to avoid shaft deflection, and wherein shim means are provided to compensate for deflection of the upper forming roll shaft.
 11. Apparatus according to claim 1, wherein the back-up and thrust sections comprise a lower roll driven at the same speed as the lower forming roll of the respective unit, and an upper roll to hold the pipe against said lower driven roll, said upper roll having a flange to bear against the pipe end and having means to exert thrust against said pipe end.
 12. Apparatus according to claim 11, wherein said lower roll is covered with a friction enhancing material.
 13. Apparatus according to claim 11, wherein said upper roll is retractable for entry of the pipe into its unit and exit therefrom, and wherein means are provided to move said upper roll vertically and to press it against the inside of the pipe to press said pipe against said lower roll.
 14. Apparatus according to claim 1, wherein said intermediate pipe supporting sections each comprise at least one pair of arms rigidly connected together in ''''V'''' relation, means to tilt said arms in one direction to permit entry of a length of pipe, means to fix said arms rigidly in upright position to support said pipe, and means to tilt said arms in the other direction to permit said length of pipe to issue from said intermediate pipe supporting section.
 15. Apparatus according to claim 14, wherein there are two pairs of said arms, said pairs being rigidly connected together and spaced apart axially of the pipe.
 16. The method of annularly roll forming both ends of a length of helically corrugated pipe issuing axially from a pipe forming machine, which includes the steps of: a. fixing the axial position of the trailing end of the length of pipe; b. feeding said length transversely of its axis into a first forming station, having a roll forming element fixed in relation to said trailing end, c. annularly roll forming said trailing end while supporting said length of pipe intermediate its ends and rotationally driving said length at both ends, d. maintaining an axial thrust against the leading end of said length during said roll forming operation, e. feeding said length transversely of its axis into a second roll forming station, having a thrust element in fixed relation to said trailing end, f. annularly roll forming said leading end while supporting said length intermediate its ends and rotationally driving said length at both ends, and g. maintaining an axial thrust against said trailing end during said last named roll forming operation. 